Action Potential Transfer at the Purkinje - Ventricular Junction: Role of Transitional Cells.

摘要

At the Purkinje (P) - ventricular (V) junction a zone of 'transitional (T)' cells is found. In the present study we investigated the role of these T cells in P-to-V conduction. Using the 'model clamp' technique, an experimentally recorded rabbit P cell was coupled to a phase-2 Luo and Rudy (LR) model cell, which in turn was coupled to a strand of phase-2 LR model cells. In our experiments, the single LR model represents the T cell, while the strand of LR models represents subendocardial V cells. This approach enabled us to change selectively coupling conductance (G(sub c)) between cells, presence of T cell, and relative size of cells. We demonstrated that: (1) a decrease of G(sub c) between P-T and T-V increases the delay of V activation, (2) the delay of V activation is importantly due to conduction between T and V cells, (3) there is a critical G(sub c) for successful conduction at the P-V junction, (4) the critical value of G(sub c) for conduction at the P-V junction is lower in presence (11.0 plus/minus 0.7 nS) than in absence (13.7 plus/minus 0.8 nS) of the T cell, and (5) enlargement of the T zone size hampers successful P-to-V conduction.